1. Field of the Invention
The present invention relates generally to methods and systems for controlling fluid flow, and more particularly to a pressure balanced valve.
2. Discussion of the Related Art
Many industrial processes require precise control of various process fluids. For example, in the semiconductor industries, mass flow controllers are used to precisely measure and control the amount of a process fluid that is introduced to a process chamber. The term fluid is used herein to describe any type of matter in any state that is capable of flow. It is to be understood that the term fluid applies to liquids, gases, and slurries comprising any combination of matter or substance to which controlled flow may be of interest.
An integral part of mass flow controllers is the valve, which regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. One such valve is a direct acting solenoid valve, which provides excellent resolution, is low cost, low power, fast acting, and small in size. While solenoid valves work great for low flows, they typically have problems when applied to control flows greater than about 100 Standard Liters per Minute (slpm). This problem occurs when the pressure forces across the metering orifice becomes a significant fraction of the solenoid pulling force and effects valve performance.
To combat the above problem, the disclosed embodiments include a pressure balanced valve that eliminates or reduces the pressure drop force to achieve reasonable valve performance for larger orifice diameters.